Fantastical photographer Tim Walker exhibits at Somerset House and tells us why every girl or boy he shoots is Alice in Wonderland

Tim Walker is one of the world's leading fashion photographers, his work stretching across as impressively broad of a spectrum as his medium allows, from sprawling and extravagant fantasy dreamscapes to simple but startlingly vivid portraits.

Now, in a new book and collection that contains not only some of Walker's most beautiful photographs from the last five years but also some of the props that built those dreams, Mulberry presents Story Teller at Somerset House, opening today. It's an exhibition that doesn't just invite the viewer to peer through the looking glass, but tumble, spiralling down the rabbit hole. We spoke to Walker ahead of the show.

Dazed Digital: Would you say that the pictures in Story Teller are the best expression of where you are and where you're heading at the moment?Tim Walker: Well, I think when you've done a show, and we started working on this eighteen months ago, even before you're done it begins to feel dated. By the time you've finished it and put the book down – it takes so long to do a book, I think we finished it a year ago and it's only just been published – when you've done all that then obviously you have a fresher point of view.

DD: How is working with Mulberry?Tim Walker: They have funded this show and I would never have been able to do more than just pictures on a wall. Just the cost of showing the films, getting the props, maintaining them and preserving them – it wouldn't have been possible without Mulberry.

DD: Did you find that their involvement compromised the narrative of Story Teller that you already had in your head?Tim Walker: There was absolutely no commercial need from them; they were like, 'Just do a show you're really comfortable with and we'll fund it as much as we can'. I put in money from my own commercial work, too, and together we created Story Teller.

DD: Do you have a favourite piece here, in the Story Teller exhibition?Tim Walker: I think it's always the latest pictures that you love the most as a photographer – there are some here that are only three weeks old, and we very much worked on that for the show. It was just me, for three days, working on location with a set designer and a 12 year-old girl; she's not a model and she's not wearing any real fashion brand. A lot of people still want to know, 'What are the commercial constraints?' But we chose every single piece of clothing because we think that it's beautiful. I haven't been forced to use anything – in my pictures someone is wearing the clothes because those clothes are right for the picture and not the other way around. It's not a struggle. Everything here is here because it works in the pictures.

DD: Given the title, Story Teller, is there a book or story that's influenced your work more than any other?Tim Walker: I think Alice In Wonderland will always run in my head: the idea of the girl who falls asleep, tumbles in to a dream world and has to find her way out. It's the best – the trippiness and the idea of the girl as the heroine. Every girl or boy I photograph is Alice.

Story Teller is at Somerset House East Wing galleries until 27th January. Story Teller the book is available now (Thames & Hudson).